What Are The Geotextile Features In Highway Engineering?

1 Characteristic of geotextiles in highway engineering

1.1 Physical properties

1) Heat resistance. The melting point of geotextile fabric at room temperature is high, which can reach 260 ℃, while the temperature of asphalt material laid on-site in the process of highway construction is 150 ℃, which is much lower than the melting point of geotextile.

2) Good strength characteristics. geotextile fabric has high tensile strength, puncture strength, and tear strength due to the use of plastic fibers as raw materials and after a complex production process.

3) Good flexibility. Geotextile is made of plastic stretched into fiber filaments many times, and processed by shearing and machine preparation, which has good deformation performance, while flexible good, folding and fracture resistance.

4) Anti-aging property. In many experimental studies, the physicochemical properties of geotextile itself are affected by environmental temperature and humidity. characteristics of geotextiles are little affected by ambient temperature and humidity; and due to the stable chemical properties, they are resistant to acid, alkali, and corrosion. Alkaline, corrosion resistance, so that it is strong anti-aging properties in practical engineering applications.

5) Good asphalt adsorption. The construction sequence of geotextile laying is: first evenly spray After sprinkling asphalt mastic oil and laying geotextile, finally laying asphalt surface layer, geotextile on leach The adsorption of geotextile on the asphalt surface layer is an important factor to ensure the overall paving effect of asphalt.

1.2 Chemical properties

1) Acid and alkali resistance. Studies have shown that geotextile fabric can maintain a good original state in different acid and alkaline environments, and the related physical and chemical properties are stable.

2) Corrosion resistance. As geotextile fabric uses plastic fiber as raw material, it is an inorganic polymer synthetic material with strong anti-corrosion resistance and strong anti-corrosion to most of the redox agents.

2 The principle of the role of geotextiles in highway engineering

With the growth of highway operation period, more and more diseases are exposed, such as network cracks, potholes grooves, cracks, etc. (see Figure 1). Cracking of road surface will affect the stability and comfort of vehicle driving. In order to solve the problem of pavement cracks, the most common method is to place asphalt mixture on the original road surface. The most common method to solve the cracked pavement is to lay an asphalt mixture cover layer on the original road surface to achieve the repair effect. Due to the long-term vehicle load and periodic environmental temperature changes caused by shrinkage deformation, structural layer relative The impact of the relative displacement of the road substrate cracks quickly reflected the overlay layer, the formation of emission cracks Cracks, not only affect the safety of road traffic but also make the surface water infiltration into the road substrate, weakening Weaken the bearing capacity of the road substrate, which will lead to the settlement and deformation of the road surface after a long time.

According to the different causes, the emission cracks can be divided into load type and temperature type reflection cracks. When the wheel load is distributed on both sides of the original structural layer crack, the original structural layer is displaced under the action of the external load. As the asphalt cover layer is closely connected with the structural layer, the displacement of the original road structural layer causes tensile stress on the surface of the asphalt cover layer, and when the tensile stress on the cover layer exceeds the ultimate tensile stress value, the bending and tensile launch crack appear. When the weight of the vehicle is concentrated in the crack side, the concentrated load side of the road structure layer due to external forces produces vertical displacement, so that the original pavement cracks on both sides of the structure of the relative displacement. The relative displacement of the original structural layer cracks above the asphalt cover layer to form large shear stress, shear stress reaches the limit stress value when shear damage occurs, the formation of damage cracks.

Existing engineering practice shows that the road structure surface and asphalt cover layer between the laying of a layer of geotextile can effectively reduce the formation of launch cracks. The main principle of the role of geotextile fabric applied in highway engineering is as follows.

1) Reduce the adhesion between the road structure surface and the asphalt cover layer. When the temperature decreases, the original road structure layer shrinkage deformation, due to the role of adhesion between the road structure surface layer and asphalt cover layer makes the surface of the asphalt cover layer concentrated tensile stress, when the tensile stress reaches the asphalt ultimate tensile strength value, the cover layer fracture. The road structure between the surface layer and the asphalt cover layer after the addition of geotextile, can reduce the structural interface between the adhesive force, reduce the cover layer subject to tensile stress.

2）Expand the force range. Highway structure due to vehicle load relative displacement difference, so that the original road cracks due to bending and settlement difference caused by asphalt cover layer shear stress concentration phenomenon, geotextile through its ductility can be extended to a larger range of stress, reduce the stress of the upper crack cover layer.

3) The role of impermeability and water barrier. in contact with asphalt mixture after mixing The closed asphalt-geotextile composite impermeable water barrier layer can prevent surface water from penetrating It can prevent surface water from penetrating the road structure grass-roots level, thus protecting the road grass-roots level. Based on the above excellent characteristics, geotextiles and other geosynthetic materials are widely used It is widely used in the repair of cracks in the road surface and the reconstruction and laying of old and new road surfaces.

In the actual project, often according to the form of pavement damage to take the surface laying of leachate, However, under the combined effect of traffic and temperature deformation load, the stress concentration in the asphalt cover layer directly above the original asphalt pavement cracks, when the stress reaches the ultimate tensile strength value of asphalt, the overlay layer cracks, and forms reflection cracks. When the stress reaches the ultimate tensile strength value of asphalt, the overlay layer cracks, forming reflection cracks, so that surface water penetrates into the road base, affecting the stability and durability of the road. The geotextile as a soft sandwich layer of old and new asphalt pavement can effectively absorb the crack location The geotextile can effectively absorb the stress at the crack location, thus reducing the generation of reflective cracks.

3.2 Application in cement concrete pavement overlay project

Cement concrete pavement is also prone to cracking under the combined effects of long-term traffic load, temperature load, and natural environment and other combined effects are also prone to cracking, breakage, and floor debonding and other Cracking is the most common. In cement concrete pavement rehabilitation projects, an asphalt mixture cover layer is often laid, but under the action of traffic load, the original cement concrete pavement due to cracking makes the road structure on both sides of the crack occur at different levels of vertical or horizontal displacement. level of vertical or horizontal displacement, which makes the original cracked upper cover layer is subject to large tensile and shear stresses.

At the same time, temperature changes caused by the original road cracks on both sides of the contraction deformation, increasing the tensile and shear stress of the cover layer, it is very easy to make the original cracks reflect the cover layer, causing the cover layer cracking damage. In the original cement concrete pavement and asphalt cover layer between the addition of a layer of geotextile dissipation interlayer, helps cover layer cracks at the stress dissipation, reduce the occurrence of cracks in the cover layer.

4 Construction technology of geotextile in highway engineering application

Select the corresponding geotextile fabric material according to the requirements of asphalt highway launch crack prevention, and operate according to the specifications.

1) Original road surface cleaning and repair. Before paving geotextile, sweep away the dust and miscellaneous soil of the original road surface, shovel flat with protrusions, for road cracks, potholes, or broken places, remove the broken part, and fill with cement concrete or asphalt repair to ensure that the road surface is dry and tidy.

2) Spraying asphalt sticky layer. In the clean original road structure on the surface layer evenly Spray 1~1.3 L/m² asphalt, and control the temperature of asphalt to prevent the temperature from being too high to affect The later geotextile paving. The asphalt spraying range should be wider than the geotextile paving range 5～10 cm.

3) Geotextile paving. Immediately after finishing the spraying of the asphalt sticky layer, the paving of geotextile is carried out by special paving machinery, and the whole process must ensure that the geotextile is flat and free of folds. The rough side of the geotextile will be facing upward, and the lap length between adjacent geotextiles should be 4~5 cm, and the asphalt sticky layer will be painted at the lap, and the next geotextile joint will be placed under the previous one. Prohibit vehicles or other machinery from driving on the newly paved road.

4) Construction of asphalt surface layer. Pour the asphalt material on the road surface and spread it evenly, then Then use the roller to roll along the direction of spreading asphalt from the roadside to the middle of the road, rolling When rolling, ensure the overlapping width of rolling. To ensure the rolling effect, the speed of rolling should be reasonably controlled. The speed of the first rolling is maintained at 1.5 to 2 km/h, and the speed of multiple rolling can be 2.5 to 3.5 km/h. 2.5-3.5 km/h.

5 Conclusion

Geotextiles have excellent tensile strength, elongation, and asphalt adsorption. It can effectively reduce the stress concentration at the cracks of the asphalt cover layer due to traffic load and temperature shrinkage deformation. stress concentration phenomenon at the crack of asphalt cover layer due to traffic load and temperature shrinkage, and extend the stress to a larger range, which can alleviate the formation of reflective cracks in the road structure is alleviated. In addition, the excellent physical and chemical properties of geotextile fabric and economical properties also make them widely used in landfill lining systems, reinforced gravel piles, and other civil engineering fields. In addition, the excellent physicochemical characteristics and economic properties of geotextiles have also made them widely used in landfill lining systems, reinforced rubble piles, and other civil engineering fields. With the development of science and technology, the technology of geotextiles such as geotextiles has been innovated. geotextiles have been innovated, their application in the field of highway engineering construction The prospect will be immeasurable